1. Field of the Invention
The present invention relates to thermally-insulated shipping containers and, more particularly, to shipping containers that are selectively inflatable. More specifically, the present invention relates to a pair of film layers having opposed reflective surfaces, and an optionally-interposed film baffle layer, that together define an inflatable envelope in the form of a flexible insulating bag.
2. Description of the Prior Art
In the transportation and distribution of products, the xe2x80x9cshipping environmentxe2x80x9d is defined by both the product and the package. While the corrugated fiber board boxes, steel drums, wooden crates, and pallets have not changed significantly over the past 80 years, the shipping requirements of the products have changed with each new generation of both product and shipping technology. As a result, packaging materials have improved to meet the demands of the new technology.
Refrigerated transportation at one time meant a horse-drawn wagon packed with ice and straw. Super-cooled gases and microprocessor-controlled motors have replaced the earlier, primitive refrigeration techniques. Reliable, temperature-controlled, surface transportation is now available to and from almost anywhere in the world. Trucks and ocean container shipping utilize positive, mechanical refrigeration systems to retard spoilage in transit.
Such surface transportation is relatively slow, and the shipped goods must have a correspondingly long shelf life. However, many temperature-sensitive products, such as perishable foodstuffs, are time-sensitive as well. Successful long-distance shipping is only feasible where transportation time can be minimized.
Servicing a worldwide food market required yet another technological developmentxe2x80x94the generous cargo holds of newer, wide-body passenger jet aircraft in the late 1960""s and early 70""s. The drop in airfreight rates heralded by these new jets for the first time permitted the cost-effective transportation of perishable, medium-value commodities such as meat, seafood, and fresh produce.
Traditionally, such perishable foodstuffs, as well as pharmaceuticals, are cooled prior to shipment, then placed within a thermal insulating material, and shipped with only a modicum of ice or refrigerant to absorb the heat that flows through the insulation. For many years, molded expanded polystyrene (xe2x80x9cEPSxe2x80x9d) containers have been the thermal insulating material of choice. The perishable goods are placed within the EPS containers, which are then in turn placed within small, corrugated shipping boxes.
EPS containers have been widely used since the lowered airfreight rates first made this form of shipment economically practical. While providing satisfactory insulation qualities as well as being light in weight, EPS also presents several negative characteristics to the shipping industry. EPS is an xe2x80x9cexpanded,xe2x80x9d non-compressible material, and consists of a very large number of small air bubbles formed in a polystyrene plastic matrix. EPS""s poor volume efficiency increases shipment costs when transporting the empty containers to the location of their use, as well as causing increased warehousing costs when stored in inventory prior to use.
While providing reasonable protection from shock impacts during transit, EPS has poor resistence to the application of puncture and shear-loading. EPS easily fractures, requiring the use of an additional plastic liner bag when shipping products with a liquid component, such as ice-chilled, fresh seafood. The lack of such an additional plastic liner risks liquid leakage from the EPS container during shipment, and the resultant expensive damage to aircraft cargo holds or other corrosion-sensitive shipping environments.
In an effort to avoid EPS and its negative characteristics, a number of shippers have attempted to make use of metalized, radiant barrier bags. Relying on the property of shiny, metalized coatings to reflectively radiate heat energy, such products have found only marginal success as insulated packaging. Although reducing warehousing and breakage expenses, as well as enjoying lower manufacturing costs, many shippers have determined that such radiant bags do not control temperatures over a sufficiently long period of time.
Ideally, it would be desirable to provide an insulative system having a reliable thermal performance over extended time periods (at least 48 hours), which is leakproof, can be shipped and stored in a manner requiring less space than EPS, and that is fabricated out of materials and in a manner that remains cost-competitive with the EPS insulated box product.
It is thus an object of the present invention to provide a flexible insulating bag of collapsible design having equal thermal insulation to that provided by EPS. The reduction in storage and shipping volume of the collapsible bag over the EPS container translates into lower costs, enabling world-wide marketing by a single source of supply, permits distributors to economically inventory large quantities of different-sized shipping container bags, and permits shippers to maintain a greater inventory, requiring fewer deliveries as well as economically ship to remote packing locations to cost-effectively service the fresh market from more remote source regions.
It is a further object of the present invention to provide two reflective surfaces, one inside the hot face to function as a low-emissivity surface and one on the inside of the cold face, functioning as a radiant barrier.
It is another object of the present invention to provide an inflatable design, permitting collapse of the insulating container for efficient storage, and, when inflated, creating an airspace adjacent the reflective surfaces to empower a further reduction in heat flow, either by lower emissivity or greater reflectivity.
It is another object of the present invention to provide an alternate intermediate baffle design that incorporates the aforementioned double radiant barrier, in an insulating system that bisects the insulating, inflated chamber in a manner that further inhibits convective heat transfer.
It is a still further object of the present invention to fabricate such an insulating bag in a manner that utilizes a minimum number of processing steps to form all air-containing and shape-controlling structural features of the insulating bag, including the incorporation of a flat inflation valve and a closure securement system, such as a zip-closure.
It is another object of the present invention to include one or more uninflated gussets within a bottom panel of the insulating bag to receive and collect melted ice water and any liquid leakage from the shipped products, separating such liquid from the products enhancing freshness and minimizing contamination.
It is another object of the present invention to fabricate the flexible insulating bags out of film materials using rf welding to enable reliable, high volume manufacturing at low per-unit cost.
It is another object of the present invention to provide a flexible insulating bag that is inflated with air for normal insulating values, or may be optionally inflated with an inert, low conductivity gas, such as argon, to further enhance insulating performance.
It is another object of the present invention to permit the collapse of a used insulating bag by deflating same, reducing disposal costs, whether shipped for recyling or on the basis of a reduced amount of landfill volume required if discarded.
These and other objects of our invention are provided by a flexible insulating bag that utilizes an inflatable wall panel construction. A pair of opposed flexible plastic film layers form the walls, and they are inexpensively attached together by rf (radio-frequency) welding. The intricate pattern of attachment seams that connect the pair of film layers is used to define the individual inflatable wall panels, as well as the overall shape of the insulating bag upon its inflation.
The inflatable walls significantly reduce conductive heat losses through the insulating bag. An enhanced insulative performance can be obtained by replacing environmental air as the inflating gas with an inert, low conductivity gas, such as argon.
Further insulating enhancement can be obtained by minimizing losses caused by radiant heat transfer. One method of achieving lower radiant thermal losses utilizes a metalized reflective layer formed on one of the surfaces of the plastic film. When configured in a manner resulting in the placement of the reflective layer on the inner surface of the outer wall (which is normally the xe2x80x9chot facexe2x80x9d), a low emissivity surface is obtained. A similar metalized surface provided on the opposing, inner surface of the interior wall film, normally the xe2x80x9ccold face,xe2x80x9d acts as a radiant barrier.
An alternate strategy for minimizing radiant thermal losses (as well as convective heat losses), makes use of baffles placed within the inflated wall panels. One type of baffle relies upon a stiffened material, and will, if carefully dimensioned, self-center between contracting adjacent attachment seams during inflation of the wall structure. Emplacement of the stiffened baffles within the wall structure during the fabrication thereof may be obtained by providing a sheet of baffle material having slots formed therein that dimensionally conform in both size and location to the rf welding seams. The slotted baffle material is then received between the pair of plastic film layers prior to rf welding.
An alternative baffle material makes use of a continuous sheet of a flexible film having both surfaces metalized and rf-weldable. When placed between the plastic, outer wall film layers and alternately attached to interior and exterior liner walls, the flexible baffle material will kink during inflation of the wall. Such alternate attachment seams can easily be obtained by interweaving the flexible baffle sheet through a comb-shaped release form that is withdrawn prior to the making of a final weld to close off the wall panels.
The use of rf welding enhances the manufacturing efficiencies enjoyed by the use of plastic film layers from which to fabricate the insulated bag. When appropriately pre-folded prior to welding, the plastic film layers and the detailed rf welding pattern jointly cooperate to minimize the number of welding passes required. Bag formation with an asymmetrical welding pattern requires two separate passes, with the second to secure the side panels together, forming the boxed ends.
Alternatively, the use of a symmetrical, single-pass welding pattern permits the formation of an enclosed bag, including all side sealing seams, and a double-flap instead of a single-flap enclosure lid. The inflatable portion of a single welding pass design is defined by a seam pattern that does not encompass the entire area of the opposing plastic film layers. Adjacent to the symmetrically-formed container floor portion are a pair of uninflated floor gussets. Upon opening the interior portions prior to receipt of the cargo to be shipped, the bottom gussets form a liquid reservoir suitable for receiving and holding any liquids as might drain from the cargo area. Such liquid drainage might be given off by the cargo itself, or result from meltwater from the cooling ice. Removal of such liquids from immediate contact with the shipped cargo reduces spoilage and extends the shipping life of the cargo.
Some further objects and advantages of the present invention shall become apparent from the following description, claims and drawings.